Cathode luminescent indicator tube having a concave grid electrode



, FUITAKEWJAKABANE ETAL CATHODE LUMINESCENT INDICATOR TUBE HAVING Oct. 6,1970

A CONCAVE can) ELECTRODE Filed Aug. 16, 1968 FIG. 2

AUAVA A A A A I) FIG.

:. f? it! I 1 1 I I... llllli INVENTORS 4 MW m M K N AA A R Kwr A m 4mm 1 gwm w A ano g Y v 7 INEOH mwmm FTHHT Y B United States: Patent (Nee 3,532,921 CATHODE LUMINESCENT INDICATOR TUBE HAVING A CONCAVE GRID ELECTRODE Fuitake Akabane, Tsunekiyo Iwakawa, Hideyo Iami,

Hiroshi Okazaki, and Toshio Wada, Tokyo, Japan, assignors to Nippon Electric Company, Limited, Tokyo,

Japan Filed Aug. 16, 1968, Ser. No. 753,248 Claims priority, application Japan, Aug. 19, 1967,

. 42/ 71,277 Int. Cl. H01j 7/42; H01k 1/60 U.S. Cl. SIS-109.5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a cathode luminescent indicator tube, and particularly to a character indicator tube provided with a hot cathode and a set of fluorescent films arranged in a pattern corresponding to characters to be displayed, wherein the character indication is performed by utilizing the luminescence emission of the fluorescent films due to electron impact thereon.

A conventional numerical indicator tube of this type, such as disclosed in Japanese Utility Model Publication No. 11865 1964, has an envelope with a viewing window, a set of fluorescent films coated on the inner surface of the viewing window and arranged in a numerical pattern to be displayed, anode electrodes, control grid electrodes, and hot cathode electrodes, these electrodes being separately disposed in order of mention towards the rear from the fluorescent layers'within the envelope.

Another type of the conventional cathode luminescent indicator tube, as is described in Electronics, May 29, 1967, pp. 212-213, has an envelope with a viewing window, a hot cathode, a space charge grid, a set of phosphor layers coated on anodes, these elements being located in order of mention towards the rear from the viewing window within the envelope. The latter cathode luminescent indicator tube is intended to have its luminescence emission from the phosphor layers observed from the front.

In the conventional cathode luminescent indicator tubes of this type, the hot cathode is linear and the grid electrode is flat. The cathode luminescent indicator tubes having such structure do not have a uniform electric field since distances from points on the grid to the cathode differ with the points, especially in case of a very large indicator tube. This results in defects since the electrons are highly concentrated at a region where the distance between the grid and the cathode is the shortest and consequently the fluorescent films cannot emit a uniform bright luminescence over the whole surfaces thereof.

An object of this invention is to provide a cathode luminescent indicator tube which is possible to obtain uniform brightness throughout the fluorescent films by eliminating the above-mentioned defects.

FIG. 1 is a perspective view of a tfirst embodiment of this invention;

FIG. 2 is a cross-sectional view taken along a line A-A' in FIG. 1,

vPatented Oct. 6, 1970 FIG. 3 is a perspective view of a second embodiment of this invention;

FIG. 4 is a cross-sectional view taken along a line B-B' in FIG. 3; and

FIG. 5 is a cross-sectional view of a third embodiment.

According to this invention, there is provided a cathode luminescent indicator tube comprising an electron emission source using a hot or cold cathode, a grid having a concave main portion which is formed by curving or folding thereof for making the distance from any point thereon to the electron emission source nearly constant, a set of fluorescent films, and anodes associated with the fluorescent films for applying a positive potential to the corresponding fluorescent films to excite them.

In the cathode luminescent indicator tube according to this invention, the grid for deriving and accelerating the electrons from the electron emission source is located at a nearly equal distance with respect to the electron emission source, so that the density of the derived electrons is almost uniform over the space between the grid and the fluorescent films, thereby generating a uniform brightness of the fluorescent films.

Referring to FIGS. 1 and 2, the first embodiment of this invention comprises a set of anodes 1 made of a conductive material and arranged in a pattern corresponding to characters to be displayed, an insulating base plate 2 of glass or ceramic to be provided with the anodes 1 thereon, a set of fluorescent films 3 coated on the correspondinganodes 1 by utilizing sedimentations, electrodeposition or a spraying technique, a cathode 4, and a mesh grid 5 of which a main portion is curved to be in concentric relation with the cathode 4 to obtain a uniform brightness. The grid 5 is formed of the combination of two flat planes and a main semicircular cylindrical surface which is arranged in concentric relation with the cathode, thus making the distance between the grid 5 and the cathode 4 constant over the whole surface of the semicircular cylindrical portion. With this arrangement, the uniformity of the anode current is practically the same as that obtained when the combination of the anodes 1, the insulating base plate -2 and the fluorescent fihns 3 take the shape of a semicircular cylinder arranged in concentric relation with the cathode 4, instead of a flat plane, and therefore no trouble is found in practical use.

The grid 5 of the second embodiment of this invention has a V-shaped cross-section as shown in FIGS. 3, and 4, and that of the third embodiment has a trapezoidal crosssection as shown in FIG. 5. These grids have nearly the same effect as the above-mentioned effect of the first embodiment.

While this invention has so far been explained, with regards to particular embodiments, the scope of the invention to be determined by the following claims.

We claim:

1. A cathode luminescent indicator tube comprising a source of electrons, a plurality of anodes spaced from the source of electrons for attracting the electrons and a plurality of fluorescent films respectively coated on the anodes located between the source and the anodes to intercept the electrons and liuninesce in response to electrons impinging thereon, and a control grid spaced between the source and the fluorescent film with the grid provided with a concave portion facing the source and located between the film and the source to assure uniform electron distribution and uniform luminescence from the film.

'2. A cathode luminescent indicator tube comprising a longitudinal radiating cathode for supplying a source of electrons, a plurality of substantially planar anodes spaced from the cathode to attract the electrons and a plurality of fluorescent films of like planar shape as said anodes respectively coated thereon to intercept the attracted 5. The device as recited in claim 2 wherein the conelectrons, cave section is open trapezoidally shaped with the open and a grid substantially coextensive in size with the part of the trapezoid facing the cathode.

film and anode and placed between the film and the cathode with the grid further having a longitudinal r References Cited concave section placed between the cathode and the 0 UNITED STATES PATENTS film with the concave side parallel to and facing I the cathode to provide uniform electron distribution and uniform luminescence from the film.

3. The device as recited in claim 2 wherein the concave section of the grid is in the form of a half-cylindrical sur- 10 JAMES LAWRENCE Pnmary Exammer face in concentric relationship with the cathode and a OREILLY, ASSistaIlt Examiner pair of planar flanges flanking the concave section and being substantially parallel to the film.

4. The device as recited in claim 2 wherein the con- 15 cave section is V-shaped with the open part of the V facing the cathode. 

